This invention relates to heart monitors and more particularly to heart monitors of the portable type.
One example of a portable heart monitor of the type herein contemplated is disclosed in commonly assigned U.S. Pat. No. 3,938,507. The monitor of the '507 patent is provided with a pair of electrodes which are configured so as to be conveniently and comfortably held within the armpits of a user in accordance with the teachings of U.S. Pat. No. 3,792,700. The preferred use of the device is in the method disclosed in U.S. Pat. Nos. 3,910,260, 4,004,577, and 4,658,830. As disclosed in the aforesaid patents, heart monitors may be used in conjunction with medicaments contained within autoinjectors for enabling a designated coronary-prone individual to self-administer arrhythmia and thrombolytic treatment drugs during the early minutes or hours of the onset of heart attack symptoms at a time before the individual can be hospitalized or reached by an ambulance crew. For this use, it is important that the monitor be capable of simple, but effective, connection with the user so as to acquire the electrical activity of the heart of the user in a form capable of transmission over a telephone line to a central source where sufficient intelligence is provided for aiding the individual in undertaking the self-administered treatment.
Portable heart monitors are also utilized as portable diagnostic tools. For this purpose, the emergency utilization of the device is not as critical as in the use described above. Typically, a portable heart monitor could be used by paramedics to monitor the heart of a patient which is being transported to the hospital. In addition, such portable monitors are quite useful in physician house calls. Moreover, portable monitors can have many uses in hospitals as well.
A limitation on the two-electrode monitor disclosed in the aforesaid '507 patent is that it is capable essentially of providing only one lead out of the twelve leads which are conventionally provided by non-portable in hospital ECG machines, see, for example, U.S. Pat. No. 3,058,458. There have been attempts to build into portable monitoring devices the capability of monitoring more than one lead. For example, in commonly assigned U.S. Pat. No. 4,862,896, the two-electrode unit of the '507 patent was made adaptable to provide more than one lead by securing the electrodes in predetermined positions within the monitor housing so as to achieve an additional precordial lead or leads. Furthermore in commonly assigned U.S. Pat. No. 4,889,134, there is disclosed a portable heart monitor which embodies three electrodes so as to enable the user to obtain leads I, II, and III with the use of the device. Particularly, when the device is used in its diagnostic mode, it is desirable to provide a heart monitor which is capable of obtaining more than three leads.